致密砂岩储层成岩相及孔隙演化过程
——以川中北部地区沙二1亚段为例

Diagenetic facies and pore evolution of tight sandstone reservoir: taking Sha21 sub-member  in the north of Central Sichuan Basin as an example 

朱讯,冯林杰,吕乐,蒋裕强,王小娟,李明秋,李雪松

中国石油西南油气田公司勘探开发研究院，四川 成都 610000 西南石油大学地球科学与技术学院，四川 成都 610000 中国石油天然气
集团公司非常规油气重点实验室，四川 成都 610000 中国石油西南油气田公司川东北气矿，四川 达州 635000）

为查明川中北部沙溪庙组沙二1亚段致密砂岩储层的演化历程，通过铸体薄片鉴定、扫描电镜观察、阴极发光、常压物性测试等方法，在明确储层特征的基础之上，对沙二1亚段河道砂岩成岩作用类型及时序进行了厘定，引入定量成岩参数对成岩相类型进行了细分，并通过增、减孔曲线叠加的方法对不同成岩相的砂体孔隙演化历程进行了恢复。结果表明：1）川中北部沙二1亚段主要发育河流相低—特低孔、超低渗致密砂岩储层；2）依据成岩参数划分出中等压实￣弱胶结￣强溶蚀相（Ⅰ）、中等压实￣中等胶结￣中等溶蚀相（Ⅱ）、强压实￣弱胶结相（Ⅲ）和弱压实￣强胶结相（Ⅳ）4类成岩相；3）成岩相Ⅰ为最有利成岩相，主要发育于边滩底部；成岩相Ⅱ为次一级的优质成岩相，常见于边滩中部；成岩相Ⅲ为不利成岩相，主要发育于边滩顶部和河床滞留沉积中；成岩相Ⅳ基本属于非储层，主要发育于河漫泥岩段，以及高泥质质量分数段附近。

In order to find out the evolution process of tight sandstone reservoir in Sha21 sub-memberofShaximiao Formation in the north of Central Sichuan Basin, the diagenesis type and sequence of channel sandstone in Sha21 sub-member are determined through the methods of cast thin section identification, scanning electron microscope observation, cathodoluminescence and normalpressure property test on the basis of clarifying the reservoir characteristics, then the quantitative diagenetic parameters are introduced to subdivide the diagenetic facies type. The pore evolution process of sand bodies with different diagenetic facies is restored through the superposition of pore increasing and decreasing curves. The results show that the reservoirs of Sha21 sub-member in this area are mainly fluvial low porosity, ultra-low and super-low permeability tight sandstone reservoirs. According to the diagenetic parameters, it can be divided into four types of diagenetic facies: medium compaction-weak cementation-strong dissolution facies(Ⅰ), medium compaction-medium cementation-medium dissolution facies(Ⅱ), strong compaction-weak cementation facies (Ⅲ) and weak compaction-strong cementation facies(Ⅳ). Diagenetic facies Ⅰ is the most favorable diagenetic facies, which is mainly developed at the bottom of point bar; Diagenetic facies Ⅱ is a secondary high quality diagenetic facies, which is commonly in the middle of the point bar; Diagenetic facies Ⅲ is unfavorable facies, which is mainly developed in the top of the point bar and the channel lag deposit; Diagenetic facies Ⅳ basically belongs to non-reservoir, which is mainly developed near the mudstone section of flood plain and the section with high argillaceous content.

10.6056/dkyqt202202022